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IEEEVehiclePowerandPropulsionConference(VPPC),September3-5,2008,Harbin,China978-1-4244-1849-7/08/$25.00○C2008IEEERealizationofanenergymanagementstrategyforaseries-parallelhybridelectricvehicleChenShanglou,WangLifang,LiaoChenglin,WanLiang,LuXinInstituteofElectricalEngineering,ChineseAcademyofSciences.Email:chenshanglou@tsinghua.org.cnAbstract—thispaperprimarilydescribesanenergymanagementstrategywhichhasbeenappliedtoaseries-parallelhybridelectricvehicle,whosefrontwheelsaredrivenbyengine-ISGhybridsystemandrearwheelsbytwowheelmotorsrespectively.Energymanagementstrategydetermineshowenergyflowsinhybridelectricvehicles,andthereforehasasignificantimpactonthefueleconomyofHEV.AfteranintroductionofthepowersystemoftheSPHEVarule-basedenergymanagementstrategyispresented.Tobettersupportthisstrategy,equivalentfuelconsumptionrateisadoptedasauniformstandardoffueleconomy.Thesituationthattheinternalcombustionrunswithlowfuelefficiencyisreducedforthemostpart.Simulationandvehicletestresultsrevealthefeasibilityoftheproposedenergymanagementstrategy.Keywords—HEV,energymanagement,modeling,HILI.INTRODUCTIONSincehybridelectricvehicle(HEV)isconsideredasanavailablesolutiontofueleconomyimprovementandemissionreductionofvehicles,manyHEVswithdifferentkindsofpowertrainsystemhavebeenintroducedtocarmarket,likePrius,Escape,Insight,etc.OneofthemostimportantissuesinHEVisthathowHEVmanagestoachievebetterfueleconomy.Generally,HEVhastwopowersources—anengineandamotor,andanenergystorage—abattery.Itisessentialtocontroltheenergyflowappropriately,forexample,howtodistributepowerbetweenengineandmotorwhenpropulsion,andwhetherthebatteryneedstochargeordischarge.Everydecisionwillhaveaneffectonthefinalfueleconomybecauseefficienciesoftheengine,themotorandthebatterychangesatdifferentoperatingpoints.Thisissueisgeneralizedasenergymanagementstrategy.Researchershaveintroducedseveralkindsofenergymanagementstrategies,likeequivalentconsumptionminimizationstrategyproposedbyPaganelliG[1],andglobaloptimalstrategyproposedbyMichielKoot[2],andsoon.However,mostoftheirworkwasbasedonmodelingandsimulation,andthereforemostoftheproposedstrategiesaredifficulttobeappliedtorealvehiclesdirectly.Moreover,theSPHEVchoseninthisstudyhasanovelpowertrainstructureandismuchmorecomplexforenergymanagementbecausetherearefourpowersourcesinthispowertrain:anengine,anintegratedstarterandgenerator(ISG)andtwowheelmotors(WM).ThusastudytothemanagementstrategyforthisSPHEVanditsrealizationinrealvehiclehassignificance.WhenanelectricmotorintheHEVworksasamechanicalpowersourceitselectricenergyeventuallycomesfromthefuelortheinternalcombustionengineinotherwords.Firstthemechanicalenergyfromtheengineshouldbeconvertedtoelectricenergyandstoredinthebatterybyoperatingthemotorasagenerator;afterwards,thiselectricenergyisextractedfromthebatterytosupplytheISGorWMandtransformedtomechanicalenergyagain.Duringthisprocess,thegeneratingandmotoringefficiencyofISGorWMaswellasthecharginganddischargingefficiencyofthebatterywillallcauseenergyloss.Thusinmostcases,directlyusingtheenginetopropeltheHEVhasadvantageinfueleconomy.However,theenginecouldbeveryinefficientincaseoflightloadorextremelylowrotationspeed,whichmakestheISGorWMapotentialsubstitute.Theproblemishowtodecidewhetherthereplacementshouldbecarryoutornot.Asaresult,theconceptofequivalentfuelconsumptionrate(EFCR)isbroughtuptoactasauniformstandardoffueleconomyforeachpowersource.Therule-basedenergymanagementstrategywouldbecomemorereasonableandeffectivebyreferringtosuchauniformstandard.Thispaperisorganizedasfollows:sectionIIandsectionIIIareaboutthedrivetrainstructureanditsmodeling;sectionIVdescribesthemethodforEFCRcalculation;therule-basedstrategyisputforwardinsectionV;simulationandvehicletestresultsareplacedinsectionVI;someconclusionsaregivenintheend.II.VEHICLECONFIGURATIONThestructureofthefour-wheel-driveHEVconsideredinthispaperisshowninFig.1.TheISGisrigidlyattachedtoaninternalcombustionengine.BoththeISGandtheengineareusedtopropelthefrontwheelsthroughthedrivetrainwhiletherearwheelsaredirectlydrivenbytwoWM.ImportantparametersofthisvehicleareshowninTable1.Figure1.ConfigurationoftheconsideredHEVIEEEVehiclePowerandPropulsionConference(VPPC),September3-5,2008,Harbin,ChinaIII.MODELINGAfacing-forwardsimulationmodeloftheconsideredHEVisdevelopedinordertoverifythepotentialenergymanagementstrategy.Sincedynamicperformanceofdrivetrainplaysalesserroleonfueleconomy,thismodelmainlyfocusesonthestaticperformanceofeachcomponentofthedrivetrain,especiallytheengine,theISG,thebattery,andthetwoWM.A.EngineThetorqueoutput(eT)andthefuelconsumptionrate(eb)oftheengineareregardedasafunctionofenginespeed(ew)andacceleratorpedalinput(Acc).Atwo-dimensionmapfromewandAcctoTeaswellasamapfromewandAcctoebisadoptedintheenginemodel,showninfig.2andfig.3.ThetwomapsderivefromaseriesofstatictestsoftheactualengineequippedtotheconsideredHEV.B.ISGandWheelMotorTheISGandtwoWMareallPMACmotorsandthusshareonetypeofmotormodel.Inthismodel,thetorqueoutput(isgTandwmT)simplyequalstotorquecommandifitdoesnotexceedthegivenmaximumtorque,otherw